1. Field of the Invention
The present invention relates to an image forming apparatus, an image forming system, and a computer program product with improved printing speed.
2. Description of the Related Art
Heretofore, an image forming apparatus is known, such as a printer that uses an electrophotographic system, an ink-jet system, a thermal system, or the like, and the apparatus is connected to an information processing apparatus, such as a personal computer (PC) that outputs predetermined print data, and prints out the print data output from the information processing apparatus onto a predetermined print sheet. In recent years, printing speed has been improved in such an image forming apparatus in order to reduce the mental stress of users, or the like.
For example, Japanese Patent Application Laid-open No. 2005-63051 discloses a technology for improving printing speed in an image forming apparatus. In the image forming apparatus disclosed in Japanese Patent Application Laid-open No. 2005-63051, if the rear edge of the print sheet currently being printed is detected by a print-sheet detection sensor, a print sheet for the subsequent page is fed in advance to a predetermined position from a feed tray that holds print sheets. In other words, in the image forming apparatus disclosed in Japanese Patent Application Laid-open No. 2005-63051, the detection of the rear edge of the print sheet is determined as the feed timing of the print sheet for the subsequent page.
However, such a print-sheet detection sensor in an image forming apparatus is arranged at some distance from a feed tray because of structural limitations. As a result, in a conventional image forming apparatus, the interval (hereinafter, referred to as a feed interval) between the print sheet currently being printed and the print sheet that is to be subsequently fed is equivalent to the distance between the print-sheet detection sensor and the feed tray at the shortest; therefore, it is difficult to improve the printing speed by further narrowing the feed interval of the print sheets.
In recent years, in order to further improve printing speed, a technology has been adapted in which the user sets in advance the sheet size, or the like, of the print sheet that is a print destination of print data via a printer driver installed in, for example, a PC, and the feed interval is determined by using the length (hereinafter, referred to as a sheet length) of the print sheet contained in the set sheet size such that the feed interval becomes shorter as the sheet length becomes shorter. Thus, it is possible to feed the print sheet for the subsequent page in advance without waiting for the detection of the rear edge of the print sheet currently being printed, thereby improving the printing speed.
In a conventional image forming apparatus, if, for example, B5 (257 mm×182 mm) size is set by the printer driver, the feed timing is determined by using a sheet length of 257 mm. However, if a print sheet of A4 (297 mm×210 mm) size is to be actually fed from the feed tray as a print sheet for the subsequent page, the print sheet of A4 size is actually fed at the feed timing on the basis of the B5 size; therefore, there is a possibility that a sheet jam is induced.